Generating electrical power in the United States from high-sulfur coal requires that the stack gases be desulfurized to comply with governmental environmental regulations. Desulfurization is frequently accomplished by contacting the stack gases with an aqueous basic nitrogen compound, for example ammonia and/or amines. However, these materials must also be removed before the stack gases can be released to the atmosphere.
Removing sulfur-containing gases by a liquid phase reaction has proved to be unsatisfactory for a number of reasons. One of these reasons is that reaction in the liquid phase is slow and becomes even slower as build-up in the liquid phase system of the absorbed contaminants reduces the absorbing capacity of the system. Another disadvantage to liquid phase systems is that the boiling point of the solvent employed limits the range of operating temperatures at which the process can be carried out. Additionally, it is frequently difficult to dispose of or regenerate the contaminated liquid by-product.